The value of crustaceans in nature.

Crustaceans can make up plankton and are food for other animals. Shrimp, lobster, crabs are a delicacy that humans eat. Some species can cleanse water bodies by eating carrion, organic debris, and decayed plants. They are an intermediate host of parasitic worms (for example, a broad tapeworm in the body of a Cyclops). Sea acorns (barnacle order) grow on the bottoms of sea vessels, and some copepods and barnacles parasitize fish, causing damage.